<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        div{
            width: 100px;
            height: 100px;
            border: 1px solid #000;
        }
        div:nth-child(1){
            background: red;
        }
        div:nth-child(2){
            background: green;
        }
        div:nth-child(3){
            background: blue;
        }
        
    </style>
    <script src="./js/test.js"></script>
</head>
<body>
    <div>Lorem ipsum, dolor</div>
    <div>Lorem ipsum, dolor</div>
    <div>Lorem ipsum, dolor</div>
    <script>
        document.write("<h1>牛</h1>");
    </script>
</body>
</html>